|Title of Invention||
"A PROCESS FOR SYNTHESIS OF POROUS CRYSTALLINE VANADIUM SILICATE"
|Abstract||A process for synthesis of porous crystalline vanadium silicate by preparing a solid mixture of silicon oxide, any alkaline gelating agent & water adding to vanadium oxide dissolved in water and a nitrogenated organic base as a gelating agent as well as a templating agent, heating in an auto-clave at a temperature in the range of 130 to 170°C under autogenous pressure to obtain crystals, separating said crystals, washing the separated crystals with water and then drying followed by calcination to obtain vanadium silicate.|
|Full Text||The invention relates to a process for synthesis of porous crystalline vanadium silicate.
Vanadium silicate prepared by the process of this invention is active for oxidation reactions using H2O2 and allow peroxo vanadium species formation which breaks and finally takes part in the oxidation reactions.
The uses of vanadium silicate according to the invention are in particular the following :
(i) Alkylation of benzene with ethylene or ethanoi and alkylation of toluene
with methanol, (ii) Disproportioning of toluene to produce para-xylene. (iii) Cracking and hydrocrackmg. (iv) Isomerization of n-paraffina and naphthalenes, (v) Reforming.
(vi) Isomerization of substituted polyalkyi aromatics. (vij) Disproportioning of aromatics. (viii) Conversion of dimethyl ether and/or methanol or other low molecular
weight alcohols in to hydrocarbon, (ix) Polymerization of compounds which contain olefine and acetylene bonds, (x) Conversion of aliphatic carbonyl compounds into at least partly aromatic
hydrocarbons, (xi) Separation of ethylbenzene front other aromatic Cg hydrocarbons, (xii) Hydrogenation and dehydrogenation of hydrocarbon, (xiii) Hydroxylation and side chain oxidation of aromatics and aliphatics. (xiv) Dehydration of aliphatic compounds containing oxygen, (xv) Conversion of olefins into compounds of high octane number.
The existing process for the synthesis of vanadium silicate by conventional method in which the source of silica and the source of vanadium are hydrorysed in alkaline medium
The existing process fw die syntfiesis of vanadhim sificate by conventional method, in which the source of silica and Ac source of vanadium are hydro^ysed in alkaline medium (pH=10.5 to 12.6) St 0**C, under a nitrogen atmosphoe and in complete absence of alkali-metal cation. Even witti ttiese precautions, a jwecqrilate of V2O5 is often observed in the starting gel, leading to tibe insufiBcient incorporatkm of vanadium in the frame work position of silicate matrix, which results into tfie material less active for catalytic reactions.
The vanadhim silicate prei^ired by sol-gel method according to the present invention, expressed m teims of molar reagent ratios, is as follows :
Molar reagent ratio Prefentbfy
SiOz/VOt 60-200 75-190
OH/SiOj 0.1-1.0 0.3-0.6
HiO/SiOi 5-25 5-15
R>f/SiOj 0.05-0.8 0.1-0.35
RN^ indicates the niHogenated organic cation derived jfrom tiie organic base used for preparing vanadium sificaHte of MFI structure according to the invention. The final VS-1 has a composition corresponding to the fomnila
XVO2 (1-x) SiOi
where X fies between 0,0001 and 0.0146, prcferaWy between 0.005 and 0.0125. The VS-i is of the Mobil Five (MFI) type, and the vanadium partially substitutes for tiie laficon. The synthetic material according to tins invention has characteristics which are evahiated from x-ray, Infrared. U.V. Visible Diffuse reflectance q>ectro8copy, ESR and model test reaction studies. The x-ray examination is carried out by means of a powder di£fractometer provided witii an electronic |R]lse counting system, using CuK -radiation. The products presented in this invention are characterized by an x-ray dififraction as shown
in (Fig-1) of the drawing acconqianying tfus specification. This spectrum is similar overall to tfie typical stlicalfte spectrum and exsctiy similar to VS-1, prepared by conventicmal mediod. Table-1 shows flic most significant q>ectral data for a VS-1 wift X=0.0125, and a idfic^ite prepared by conventional proems.
A large proportion of the tnlerplanar ^stances for the VS-1 are, even tfioi^ sfis^dy, tendentially greater than the corre^tonding distances for the pure siticafite in accordance with the hi^er foreseeable vahie of the V-O bond distance witfi respect to that of the Si-O bcmd distance. Also, sificaHse (Monocfinic structure) and VS-1 (AVI) (or&oihomHc) and its transfonnation depends on tfte ciUoff limit of vuiadhmi concentration in the starting ff^ TaUe-1.
The VS-1 (Wl) shows a characteristic IR absorption band at about 967 cm"^ (Fig-2), which is not present in the pure silicafite spectrum and is also absent in vanadium oxides and different vanadates.
The intensity of the band at 967 cm"' increases with the quantity of vanadium which substitute for the silicon in the silicalite structure
VS-1 (Wl) is of the morphology of MFI. EDAX examination has demonstrated that the vanadium distribution within the crystal is uniform which ascertains that the vanadium substitute the silicon in the silicalite structure, and is not present in other forms. The adsorption isotherm determined by the BET with N2 shows a very high surface area (450-500) m^g and has the typical behavior of a molecular sieve with a micro pore volume of 0.16-0.18 cm"^ g'\ This material was also found to be hydrophobic in nature.
The chemical and catalytic properties of VS-1 (Wl) can be modified by introducing other substituting elements such as B, A!, Fe, Ti etc. during the synthesis stage.
Accordingly, the present invention relates to A process for synthesis of porous crystalline vanadium silicate having general formula.
XVO2, (1-X)Si02 Wherein X Is a number between 0.0001 and 0.0146, which comprise :
a) preparing a solid mixture of silicon oxide, any alkaline gelating agent & water adding
to vanadium oxide dissolved in water and a nitrogenated organic base as a gelating
agent such as herein described as well as a templating agent in following molar
SiOaA/Os from 60 to 200,OH/SiO2 from 0.1 to 1.0, H20/Si02 from 5 to 25, RNVSiO;
from 0.05 to 0.8
wherein RN* is the cation of the nitrogenated organic base,
b) heating in an auto-clave at a temperature in the range of 130 to 170°C under autogenous pressure to obtain crystals,
c) separating said crystals, washing the separated crystals with water and then drying followed by calcination to obtain vanadium silicate.
The organic base is a tetraatky! ammonium hydroxide, and tetrapropyl ammonium hydroxide is preferred.
The dried sol gel is wet impregnated with the organic base which acts as a structure directing agent The wet-solid is subjected to hydrothermal treatment in an autoclave at a temperature of between 130° and 200°C, under autogeneous pressure, for a time of 1 to 2
d^ untill the crystals of ^e VS-1(WI) are obtained. These are separated from the mother solution, carelulty washed wi& water and dried.
In the anhydrous state they have the following composition XVOj : (1-X) SiOj ^ 0.05 (RN*)20. The precursors crystals are heated for 1 to 72 hours in air at 550**C in order to completely eliminate the nitrogenated at^sa& base. The final VS-l(WI) has the composition : XVO2 (1-X) SiOj. Where X is ah'eady defined. Physico chemical examinatiOTis were cairied out on the products thus obtained.
The following examples are given in order to better iSustrate tite invention but widiout limiting it in aiQ' way.
45.5 g. of tetraethyl orthosilicate are |^ed in a polyethylene beaker fitted with a mechanical stirrer. Slowly, 0.05 to 1(M) HCl was added followed by 0.6 g. of vanadyl sulfate trihydrate (VOSO4.3 H2O) (Aldrich) in 2S.0 g. of deionised distilled water under vigorous stirring for about one hour. There after the solution is heated carefully in order to accelerate hydrofysis and evaporate die tits^ alcohol which is released. After about 1 hour at 80*^0, the alcohol is completely eliminated. The gelatin point is then reached by adding a 1.0-1.5 g. of tetraa%l ammonium hydroxide per gram of SiQ2 (preferably tetrapropyl ammonium hydroxide). The gel is then dried over night at llO'C after tihorou^ washing until] it gives the negative test for chloride ions.
The wet inq^regnation is then done by adding 1.5 to 2.5 g. of TPAOH (per gm. of SiOj). The amount should be just enough to wet the solid mass con^letely. The wet soHd is flten transferred to an autoclave. The mixture is heated to 165^C under its own pressure for 1 days. Wl^n the treatment is fini^ied, die autodave is cooled, the contents are discharged and mass of the fine crystals obtained is recovered. This is carefully washed on
a filter paper widi deionized distifled water several times. Hie product is dien dried and fina&y calcined at SSO^C for six hours.
The x-ray diSraclion spectrum for the calcined product corresponds to that of VS-1 (WI) given in Fig-1.
This example illustrate the preparation of VS-1 (WI) using Ammonia solution as the gelattng agent. Since, gelation is possible with any alkaline material if it is done under controlled condition. 22. S g. of tetraetl^t orthosiHcate is placed in a beaker (Poly Etl^lene) was first hydrofyzed at room temperature vnAi a 1.0-0.05 (M) HCl for 45 minutes while stining. The solution was cooled at 0'*C and dien gradually 0.3 g. of vanadyl sulfate trihydrate (VOSO^.S H2O) in 10.0 g. of double distilled water imder vigorous stining at O0C for about 1 hours. The Ammonia sohitton was added in the cooled sohiticm under vigorous stirring. The gel point reached at about 0.5 to 0.8 g. of NH4OH per g. of SiOi. The gel is ttica dried overwei^t at 110'C alter thorougji washing untiU it gives the negative test for chlorine.
The wet impregnation is Ihen done by adding 1.2 to l.S g. of tetrapropyl ammonium hydroxide (per g. of SiOi). This amount is just enou^ to wet the soHd mass completely. The wet soKd is tfien transferred to an autodave and was heated at 160°C for 2 days. When the treatment is completed, the autoclave is cooled, the contents are discharged and the ctystals are recovered by filtration. The obtained mass was thorou^iiy washed, dried and finally calcined at 530*^C for 5 hours.
The x-ray diffraction spectrum of the calcined product corresponds to that of VS-1 (WI) and is found to be properly crystallised pure VS-1.
Operating under die c
WI - Wetness Biqnegnation C = Conventional A Amorphous
We claim ;
1. A process for synthesis of porous crystalline vanadium silicate having genera! formula.
XVO2, (1-X)SiO2 Wherein X is a number between 0.0001 and 0.0146, which comprise :
a) preparing a solid mixture of silicon oxide, any alkaline gelating agent & water
adding to vanadium oxide dissolved in water and a nitrogenated organic
base as a gelating agent such as herein described as well as a templating
agent in following molar ratios:
SiO2/VO2 from 60 to 2DO,OH/SiO2 from 0.1 to 1.0, H2O/SiO2 from 5 to 25,
RN+/SiO2from 0.05 to 0.8
wherein RN+ is the cation of the nitrogenated organic base,
b) heating in an auto-clave at a temperature in the range of 130 to 170°C under
autogenous pressure to obtain crystals,
c) separating said crystals, washing the separated crystafs with water and then
drying followed by calcination to obtain vanadium silicate,
2. A process as claimed in claim I, wherein source of vanadium oxide used is vanadium sulfate trihydrate VOSO4, 3H2O,
3. A process as claimed in claims 1 and 2, wherein the nitrogenated organic
base is Tetra propyl Ammonium hydroxide (TPAOH) of 1 (M) concentration.
4. A process as claimed in claims 1 to 3 wherein the source of silicon oxide
used is fumed silica, colloidal silica and sodium silicate sol.
5. A process as claimed in claims 1 to 4 wherein alkaline gelating agent used
is Tetrapropyl ammonium bromide, Triethy!butyle ammonium
bromide, Ethonalamine, Morpholine, Di-propylamine, triamine,
PyrroHdine, Grycerol, Phthalocyanine and NH3+ alcohol.
6. A process for synthesis of porous crystalline vanadium silicate substantially
as herein described with reference to the examples.
|Indian Patent Application Number||799/DEL/1997|
|PG Journal Number||31/2009|
|Date of Filing||27-Mar-1997|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001, INDIA|
|PCT International Classification Number||B01J29/02|
|PCT International Application Number||N/A|
|PCT International Filing date|